1. Field of the Invention
The present invention relates to diallyloxyacetic acid and its basic addition salts, their preparation process and their application as cross-linking agents.
Cross-linking agents are currently used to access polymers showing particular or improved properties. They are generally employed in weak proportions and it is hoped that they lead to homogeneous cross-linked polymers. They must therefore possess adequate properties of solubility, of reactivity, of compatibility towards the monomers or polymers with which one wishes to react them.
2. The Prior Art
It is known that cross-linked polymers are easily obtained by radical-like polymerization, notably in solution or in suspension, of one or more ethylene monomers in the presence of an appropriate cross-linking agent, containing at least two polymerizable ethylene functions such as the di- or polyvinyls compounds, di- or polyesters of, mono- or polycarboxylic ethylene acids with polyols, bisacrylamides such as N,N-methylene bisacrylamide or bisacrylamidoacetic acid. Among all these known polyethylene cross-linking agents, salified bisacrylamidoacetic acid is, to the knowledge of the Applicant, the only one which is very soluble in water but it is a derivative of acrytamide which due to its toxicity one would prefer to be absent in certain particular uses.
Therefore a hydrosoluble diethylene cross-linking agent is sought which is compatible notably with acrylic acid or its ammonium salts or alkali metals, which does not have an acrylamide fragment in its structure, for the manufacture of cross-linked polymers, insoluble in water but capable of being water-swellable such as thickening or super absorbent polymers notably intended for cosmetic and/or hygienic uses, such as the manufacture of babies diapers.
Sodium diallyloxyacetate has already been prepared by L. Holmquist, Acta Chem. Scand., 1969, 23, 1045-52, by condensation of dichloroacetic acid with excess sodium 2-propene-1-olate, in order to test its possible inhibiting activity on the neuraminidase of vibrio cholerae. Moreover allyl diallyloxyacetate is described in the American U.S. Pat. No. 4,454,065 and in the European Patent Application No. 0,094,815. In these documents, it is noted as having a boiling point of 55.degree.-60.degree. C. under 16 mm/Hg which is very different to that found by the Applicant.